I see Gartner have identified 10 pitfalls of EA - http://www.tradingmarkets.com/.site/news/Stock%20News/2507730/.
It is quite useful (and better than their effort last month) however I think it is wrongly factored - and there are really three things (Like most areas it requires: right people, process and technology) based on the right focus.
a) The Wrong Lead Architect i.e. right person
b) Insufficient Stakeholder Understanding and Support (Technical and Business) i.e. right focus
c) Not Establishing Effective EA Governance Early i.e. right process
d) Right technology [which Gartner fail to identify - presumably for fear of alienating some of their major sponsors]
The rest are simply manifestations of these things i.e.
1. The Wrong Lead Architect - to often "Architects" have primarily self-selected to deal with technology not people and is the role of EA moves from applying knowledge to managing knowledge across the enterprise stylist changes are required.
2. Insufficient Stakeholder Understanding and Support: when people outside the EA team don't use knowledge organised by the EA team in projects (and they don't gather data from projects). This requires clarity regarding the roles of EA and SA (and other elements in the enterprise) and for the EA team to realise they are NOT the primary audience of EA (and in fact can't do EA - alone).
3. Not Engaging the Business People: this is an extension of the problem above.
4. Doing Only Technical Domain-Level Architecture: this is usually caused by 1.
5. Doing Current-State EA First: This is usually because people don't realise that most knowledge in a EA should accrete as by product of business as usual.
6. The EA Group Does Most of the Architecting: This is result of 1 and 2.
7. Not Measuring and Not Communicating the Impact: This is failure to look at the communciations and governance issues (i.e. is a by-product of 9)
8. Architecting the 'Boxes' Only: This is really comes from 1 & 6.
9. Not Establishing Effective EA Governance Early: yes
10. Not Spending Enough Time on Communications: Communications is really part of the governance process